The present invention relates to the field of computers. More specifically, the present invention relates to network security.
A distributed denial of service (DDoS) attack consists of an entity installing malicious code on a massive number of machines (e.g., 10-30 thousand machines), either directly or through propagation, that overwhelms a target network element with requests. The overwhelming number of requests consumes an enormous amount of the victim network element's resources. Thus, the victim network element is unable to respond to legitimate requests.
Some existing defense mechanisms attempt to verify the legitimacy of network addresses of incoming packets. Although such mechanisms may eliminate packets with spoofed network addresses, they do not defend against other means for delivery of a DDoS attack. For example, a DDoS attack delivered via compromised machines cannot be defended against since the compromised machines are using real network addresses.